Conventionally, there are proposed various battery temperature regulating devices that can regulate a temperature of a battery group formed as a result of series-connection of battery cells that can perform discharge and charge (see, for example, Patent documents 1 to 3).
Specifically, in Patent document 1, there is disclosed a proposal to flow a charging current through a resistance for equalized charge and to use heat energy produced in the resistance for the temperature rising of the battery group in order to quickly raise the temperature of the battery group.
To limit a variation in capacity of electricity stored SOC (state of charge) in each second battery due to temperature variation between secondary batteries constituting a battery group, a proposal to limit a charging power of the secondary battery to a predetermined power that is not dependent on temperature in a case of a great temperature difference between the secondary batteries is disclosed in Patent document 2.
In Patent documents 3, there is disclosed a proposal that a cell discharge current is made larger than a cell group discharge current to limit unnecessary discharge from a battery cell at the time of equalization of the battery cells constituting a battery group.
However, in the above-described Patent documents 1-3, a configuration for performing charge/discharge and temperature regulation of each battery cell in a battery group by series-connection of the battery cells is only disclosed. There is no consideration of charge/discharge and temperature regulation carried out for each battery group in a battery pack configured by parallely-connecting the battery groups.
On the other hand, in Patent application No. 2010-82219 (hereinafter referred to as an earlier application example), the inventors have previously proposed, for example, a battery control system that can perform charge/discharge and temperature regulation for each battery group in a battery pack.
Specifically, the earlier application example includes a first switching means that switches into a state in which charge/discharge is possible for each battery group, a second switching means that switches into a state in which temperature regulation is possible for each battery group, and a control means that controls the first switching means and the second switching means. In accordance with the temperature and capacity of stored electricity of each battery group, charge/discharge and temperature regulation of each battery group are switched by the control means.
However, in the earlier application example, there is an issue that a large amount of energy (e.g., heat energy) needs to be given from the outside every time the temperature regulation is carried out for each battery group and it is difficult to save energy.